Herpesviruses are responsible for a large number of diseases, which can affect different collectives at a greater or lesser extent and that can become particularly severe in immunocompromised subjects such as, for example, premature infants, elders, transplanted patients or patients infected with the human immunodeficiency virus (HIV). Oral and genital infections by herpesvirus are of special relevance.
Herpesviruses belong to the family of Herpesviridae and are DNA type virus. They are constituted by a DNA chain surrounded by an icosahedral capsid, which, in turn, is surrounded by a tegument and a membrane disposed as a coating.
Eight different species have been identified among the herpesviruses: herpes simplex virus type (HSV-1), type 2 (HSV-2), varicella zoster virus (VZV), Epstein-Barr virus (EBV), cytomegalovirus (HCMV) and herpesvirus type 6 (HHV-6), 7 (HHV-7) and 8 or Kaposi's Sarcoma herpesvirus (HHV-8, KSHV).
All of them share the common feature that, after infection, they may remain in a latent state, alternating latent periods with reactivation periods throughout the whole life of the infected individual. The latent period is characterized by a minimal expression of the viral gene and the absence of synthesis of new viruses.
Usually a distinction can be drawn between primary infection, referred to the first infection of the subject by the virus, which usually occurs in childhood or adolescence and which is often asymptomatic, and the subsequent reactivations which lead to recurrent injuries. These reactivations occur in an unpredictable way, but there exist some triggering factors, such as illnesses, physical or mental stress situations, hormonal changes, ultraviolet radiation, or corticoids use, among others. Both primary and recurrent infections can be relatively mild, but under certain circumstances they can become fatal to the host.
Diseases caused by herpesvirus infection are diverse due to the variety of the viruses and also because most of them can interact with the infected patient in more than one way and cause more than one pathology.
Thus, for example, the VZV virus is the responsible for varicella as a primary infection, whereas the reactivation of the latent virus in adults leads to herpes zoster. Herpes zoster affects the peripheral nerves and the skin, and can show serious complications, especially in individuals with alterations in their immune system.
EBV virus is the cause of infectious mononucleosis, particularly in teenagers. The EBV latent infection can be reactivated, especially in HIV-positive patients, resulting in the hairy leukoplakia. Also, the infection by said virus can lead to malignant lesions such as nasopharyngeal carcinoma, Burkitt's lymphoma, B cell lymphoma or oral carcinoma.
Cytomegalovirus infection can lead to the perinatal disease, acute HCMV infection, and to the worsening of opportunistic infections in immunocompromised patients, e.g. transplanted patients or HIV infected patients.
The most frequent herpesviruses are herpes simplex HSV-1 and HSV-2, which are responsible for a large variety of infections involving vesicular eruptions on the skin and mucous membranes, and that can also occasionally affect the central nervous system and visceral organs.
HSV-1 infection is mainly associated with the orofacial region, causing infections from mild, such as herpes labialis, to severe, such as viral encephalitis. The most common injury associated with HSV-1 is the herpes labialis, although it can also cause other pathologies such as, for example, primary herpetic gingivostomatitis, recurrent intraoral herpes and ocular herpes simplex.
HSV-2 causes injuries that are similar to oral herpes, but which occur mainly in the genital region (genital herpes), although it may also be involved in herpes labialis. HSV-2 infection can be transmitted to newborns during delivery, so that a significant percentage of infants born from women with genital herpes become infected with HSV-2, and many of them suffer serious defects induced by the virus. The genital herpes has been associated with an increased risk of HIV transmission, and vice versa, due to the presence of genital ulcers.
Exceptionally, the reactivation or primary infection with herpes simplex virus can cause other serious and high mortality diseases, such as pneumonitis, hepatitis, tracheobronchitis or disseminated infection.
At present, the most widely used therapy for treating herpesvirus infections is aciclovir, particularly for genital herpes, herpes labialis or herpes zoster, and it may be administered topically, orally or intravenously, depending on the type and severity of the pathology. Other antivirals that are also used as antiherpetics are, for example, valaciclovir, famciclovir, penciclovir, ganciclovir, foscarnet, and cidofovir, among others.
These drugs are not actually a cure that completely eliminates the herpesvirus infection from the organism, but rather they are used to mitigate the infection outbreaks, to help to reduce the pain and to make the symptoms disappear faster.
However, none of these drugs has proved to be totally effective. Furthermore, all of them involve certain side effects. For example, locally administered aciclovir can cause irritation and burning, while when it is administered orally, it can sometimes lead to gastrointestinal disorders, headache and less frequently, renal failure or neurotoxicity.
Moreover, the continued use of antiviral drugs may cause resistances, and a lack of efficacy in the long term. That is why it is necessary to provide new alternative drugs for the treatment of herpesvirus infections, which are safe and do not cause undesirable side effects.
In this regard, in the prior art there have been disclosed different approaches for the treatment of infections caused by herpesviruses, with less side effects, using therapies of natural origin based on the administration of certain amino acids and/or peptides.
Thus, for example, in the article A. R. Gaby, Natural Remedies for Herpes simplex, Altern. Med. Rev, 2006, 11 (2), 93-101, some alternative or complementary therapies to aciclovir are mentioned for the treatment of herpes simplex infections, among them the treatment with the amino acid lysine, which exerts an antagonistic mechanism on arginine, which is an amino acid required for the replication of herpes simplex virus.
The international patent application WO-A-2007/016450 relates to the use of the amino acid glutamine, or its analogues, conjugates and derivatives for the treatment or prevention of the reactivation of herpes infections, for example those caused by HSV-1 and HSV-2. Although this document relates mainly to the amino acid glutamine as such, short peptides containing glutamine are also included, for example, Gly-Gln, Ala-Gln or Gly-Gly-Gln.
In the book chapter H. Jensen, Antimicrobial activity of lactoferrin and lactoferrin derived peptides, in: Dietary Protein Research Trends, J. R. Ling, editor, Nova Science Publishers, New York, 2007, Chapter 1, pages 1-62, it is described how lactoferrin protein present in the milk serum, as well as some specific peptides derived therefrom, have antiviral activity against, among others, the HSV-1 and HSV-2 viruses.
In the German patent application DE-A-3922453 an extract prepared from a hydrolysate of the milk serum proteins is disclosed, which has antiherpetic properties. The proteins from which the hydrolysate is prepared can be alpha-lactalbumin, lactoferrin, beta-lactoglobulin, lysozyme, or serum albumin, all of them present in the milk serum. First, these proteins are hydrolysed with at least one protease, for example, papain, pancreatin or chymotrypsin, and the residue obtained is extracted with a nonpolar solvent such as petroleum ether, benzene or toluene.
In the international patent application WO-A-92/17191 it is disclosed the use of the dipeptide L-Glu-L-Trp, called Thymogen®, for the treatment, in general, of opportunistic infections in immunocompromised patients, and in particular also for the treatment of herpes.
In the prior art, many specific peptides have been disclosed, having different sequences, which have activity against herpes viruses. Its structure is often derived from certain viral proteins responsible for the replication of herpes virus.
Thus, in the article DeMaubeuge et al, Thymopentin treatment of herpes simplex infections. An open, monitored, multicenter study, Surv. Immunol., 1985, 4 (Suppl.1), 30-36, a clinical study is disclosed with patients suffering from herpes labialis and genital herpes, to whom the thymopentin product was administered subcutaneously, so that a clear improvement was observed. Thymopentin is a pentapeptide with immunoregulatory properties whose sequence (Arg-Lys-Asp-Val-Tyr; SEQ ID NO:1) corresponds to the residues 32-36 of the protein thymopoietin.
In the British patent GB-A-21 85024, peptides inhibitors of the enzyme ribonucleotide reductase are disclosed, which contain a portion of the sequence of this enzyme, and which exhibit antiviral activity against herpesviruses. Among them the following peptides are disclosed: NH2-Tyr-Gly-Ala-Val-Val-Asn-Asp-Leu-COOH (SEQ ID NO:2), and NH2-Tyr-Ala-Gly-Ala-Val-Val-Asn-Asp-Leu-COOH (SEQ ID NO:3).
In the European patent application EP-A-0246630 certain peptide structures are disclosed such as, for example, the nonapeptide having the sequence H-Tyr-Ala-Gly-Ala-Val-Val-Asn-Asp-Leu-OH (SEQ ID NO:4), which possesses antiviral activity against herpes simplex virus.
In European patent application EP-A-0292255 it is disclosed that the pentapeptide Val-Val-Asn-Asp-Leu (SEQ ID NO:5) has antiviral activity, and that other larger peptides, which contain this specific sequence, also show the same activity.
The U.S. Pat. No. 5,859,187 relates to peptides with antiviral activity, based on fragments of the amino acid sequence of the enzyme DNA polymerase of the HSV, which are able to inhibit the activity of this enzyme. The preparation of several peptides is disclosed as, for example, H-Ala-Pro-Gly-Asp-Glu-Pro-Ala-Pro-Pro-Tyr-NH2 (SEQ ID NO:6).
In the international patent application WO-A-92/14751 a series of peptides are disclosed with activity against the virus HSV-1 and HSV-2, varicella zoster virus, human cytomegalovirus or Epstein-Ban virus. Among them, the following peptides are disclosed as particularly preferred D-Ala-Ser-Thr-Thr-Thr-Asn-Tyr-Thr-NH2 (SEQ ID NO:7), Ala-Ser-Thr-Thr-Thr-Asn-Tyr-Thr (SEQ ID NO:8), D-Ala-Ser-Thr-Thr-Thr-Asn-Tyr-Thr (SEQ ID NO:9), D-Ala-Ala-Ser-Ser-Ser-Asn-Tyr-Met (SEQ ID NO:10), Thr-Asp-Asn-Tyr-Thr (SEQ ID NO:11), Thr-Thr-Ser-Tyr-Thr (SEQ ID NO:12), Thr-Thr-Asn-Tyr-Thr (SEQ ID NO:13).
In the international patent application WO-A-93/21941, peptides comprising at least 6 amino acid residues are disclosed, which have activity against herpes simplex virus thanks to their ability to inhibit its replication. Preferably, the amino acids are in the (D) configuration and the following peptides are particularly highlighted: D-[Arg-Lys-Lys-Arg-Arg-Gln-Arg-Arg-Arg] (SEQ ID NO:14), D-[Arg-Arg-Arg-Arg-Arg-Arg-Arg-Arg-Arg] (SEQ ID NO:15) and D-[Arg-Arg-Arg-Gln-Arg-Arg-Arg-Arg-Arg] (SEQ ID NO:16). These products are preferably administered by injection, as well as topically or orally.
In the international patent application WO-A-95/1 5766 peptide derivatives with antiviral activity are disclosed, which consist of seven amino acids, including the following sequence: Arg-Arg-Trp-Trp-Cys-Arg-X (SEQ ID NO:17), where X is an amino acid or an amino acid derivative that contains a chiral center.
In the international patent application WO-A-98/04707 some antiviral agents are disclosed showing a mechanism based on preventing the association between two viral proteins required for the DNA replication of HSV virus. Several peptide sequences are disclosed, corresponding to a portion of the protein UL8 of HSV-1 virus, for example, IELVFTGVLAGVWGEGGKFV (SEQ ID NO:18).
In the international patent application WO-A-01/57072 some peptides with the capacity of crossing lipid membranes are disclosed, which exhibit antiviral activity against herpes simplex virus. Several sequences that show such activity are cited, for example, NH2-RRKKAAVALLPAVLLALLAP-COOH (SEQ ID NO:19).
In the international patent application WO-A-2006/0 18431 it is disclosed that the peptide designated as Hervip, which consists in the amino acid sequence 112-147 of human β-hemoglobin, has activity against herpes simplex virus. This peptide corresponds to the following sequence of 35 amino acids: NH2-VCVLAHHFGKEFTPPVQAAYQKWAGVANALAHKYH-COOH (SEQ ID NO:20).
In view of the wide variety of solutions described in the prior art regarding the use of peptides in the prevention and/or treatment of the infections caused by herpesviruses, it appears that a satisfactory solution has not yet been found.
Thus, there remains a need to develop new compositions and methods for treating herpesvirus infections which are effective and practical, and that are also safe, so that they involve a minimal risk of side effects.